Air and oil cylinder



nited States ABSTRACT OF THE DISCLOSURE There is herein disclosed acombination oil-air cylinder in which air exhausted from the aircylinder in a manner causing cooling of the air is used to cool the oilcylinder and in which valve means in the oil cylinder control the rateof fiow of oil in a new and improved manner.

This invention relates to control devices of the type utilized to impartmovement to and control movement of power operable machinery. Moreparticularly, this invention relates to a combination oil-air cylinderby which a press unloading device or the like may be moved betweenoperative positions and whereby the movement between the positions maybe controlled.

This invention is adapted for use with a swinging arm type pressunloader as shown in prior Patents US. 3,206,- 040 and US. 3,204,783. Inprior art apparatus of this type, an air cylinder has been provided tomove the swinging arm between a down position adjacent a die cavity in apress and an up position spaced outwardly therefrom. A separate oilcylinder has been provided to control the rate of return of the swingingarm from the up position to the down position. The primary object of thepresent invention is to provide new and improved means for controlling aswinging arm type unloader. In general the inventive features reside inthe provision of a combination oil-air cylinder by which several priorart problems have been eliminated or substantially overcome and by whichease of manufacture, ease of assembly, and reliability in use have beenincreased.

Referring now to the drawing, an illustrative embodiment of the oil-aircylinder is shown in side elevation, partly in section, with anassociated fluid control system shown diagrammatically.

Referring now to the drawing, an air cylinder and an oil cylinder 12 aremounted in telescoped relationship concentrically about a common centrallongitudinal axis 14. The air cylinder 10 comprises a cylindricaltubular member 16 and spaced end caps formed by wall members 18, 20which define a cylindrical chamber 22. The end wall portions 18, 20include annular disc portions 22, 24 which, in the preferred embodiment,fit within the end portions of the tubular member 16. The outer ends ofthe end wall members 18, 20 may be enlarged and of polygonal shape asindicated at 26 to receive fastening devices 30 such as tie rods forsecuring the end Walls and mounting bolts or the like by which theair-oil cylinder may be fixedly mounted relative to the swinging arm.

An air inlet port 32 is provided at one end of the air cylinder and anair outlet port 34 is provided at the other end. A supply of highpressure air 36 is connected to the inlet port 32 through a conventionalcontrol valve 38 which is adapted to selectively connect a supply line40 to an inlet line 42 at predetermined times in a cycle of operation ofthe press unloading machine with which the air-oil cylinder is to beassociated. An exhaust line 44 is provided to connect the exhaust port34 to the inlet line 42 or to atmosphere via line 45 through the valve38 at preselected times.

A piston means in the form of an assembly 44 is reciprocably mounted inthe air cylinder chamber 22 and atent O 3,399,603 Patented Sept. 3, 1968divides the air cylinder chamber into variable volume upper and lowerchamber portions. The piston assembly is slidably mounted on a centrallongitudinally extending support rod means 46 which is fixedly mountedin the plate 20. The piston assembly comprises a bronze bushing or thelike 48 mounted in and supporting a cap element 50. A spacer disc 52 ismounted about the cap element 50 and slidably engages the inner surfaceof the air cylinder chamber as indicated at 54. A conventionalcup-shaped packing 56 is secured on the piston assembly by a pistonfollower plate 58. A backing plate 60 abuts the spacer plate 52 andthreadably receives suitably fastening elements 62 by which the elementsof the piston assembly are securely fastened to one another.

The piston assembly 44 is formed integrally with and is part of the oilcylinder 12 which extends through and defines part of the upper chamberportion of air chamber 22. The oil cylinder is formed by an elongatedcylindrical tubular member 64 which is closed at one end by an annulardisc portion 65 of the cap element 50 of the piston assembly and at theother end by an annular end plate 66 to define a cylindrical chamber 68.The tubular element 64 is slidably movable longitudinally within the aircylinder 16 relative to the support rod 46 and in effect acts as apiston rod for the piston assembly 44 to which it is fixedly attached asby suitable welds or the like. The cylinder 64 is slidably supported ina bushing means in the form of a bearing sleeve 71 mounted within theend plate element 18 and the support plate 26. The bearing sleeve 71 isprovided with a plurality of longitudinally extending circumferentiallyspaced slots 76 for a purpose to be hereafter described in detail.

Support rod 46 is securely fastened in the plate 20 and includes ashoulder portion 78, which abuts the end plate 20, and a reduceddiameter shaft portion 80 which extends into a correspondinglydimensioned hole 82 in the end plate. The end 83 0f the shaft portion 80extends beyond the end plate 20 and is threadably secured by means of athreaded nut arrangement 84. The other end 85 of the support shaft 46 isprovided with a reduced diameter portion 86 providing a shoulder 88 onwhich a valve body means in the form of valve disc body element 90 issecured by means of a valve supporting sleeve 92 and a threaded fastenerarrangement 94 to divide the oil cylinder into variable volume upper andlower chamber portions. A further reduced portion 96 of the support rodextends beyond the threaded fastening means 94 and terminates in achamfered end portion 98 which is adapted to be matingly slidablyreceived within a correspondingly dimensioned chamber 100 in a capsleeve element 102. The entrance 104 to the chamber 100 is similarlychamfered to facilitate sliding engagement. A sealing groove and O-ring108 are provided to effect a seal between the shaft portion 96 and thesleeve 102 in the engaged position shown. Chamber 100 terminates in apassage 110 in a rod like extension 112 by which the movable cylinder 64may be connected to the machine to be operated. A removable fill cap 114is provided in the end of the passage 110 to enable the oil cylinder 64to be filled.

A flow controlling valve assembly is provided in the oil cylinder andincludes a plurality of oil passages 122 extending longitudinallythrough the valve body 90. Valve means in the form of a valve plate 124is slidably mounted on the valve sleeve 92 on support rod 46 and ismovable between an open position, as shown in the drawing, permittingflow of oil through the passages 122 and a closed position in abuttingengagement with the adjacent side surface of the valve body 90 andclosing the passages 122. A bypass 126 of reduced diameter may beprovided to enable flow in either direction at certain times. Oil flowbetween opposite sides of the valve plate 90 is also provided by acentral longitudinally extending passage 128 in the support rod 46 whichterminates at one end at 130 and at the other end in transverse passagemeans 132. The rate of flow of oil through the passage is controllableby means of a conically tipped control rod 134 which extends within anextension 136 of the passage 128 to the other end of the air-oilcylinder. Control rod 134 is connected, as at 138 to an adjustment rod140 which is provided with tool receiving means 142 for makingadjustments and fastening means 144 for securing the rod in any of aplurality of adjusted positions.

An O-ring seal 150 is provided to prevent leakage of oil from passage136. The piston assembly 44 is sealed on the support rod 46 by means ofspaced sealing assemblies 152, 154 which are identical but reverselypositioned. Each sealing assembly comprises a plurality of packingelements 156, a spacer 158, and wafer type spring means 160. SuitableO-ring seals are provided as necessary between the bushing 48 and thecap 50, between the end cap 50 and the cylinder 64, about the supportshaft 46, and between the end plate 20 and the wall of cylinder Wall 10.Thus, the air cylinder chamber 22 is substantially airtight between thepiston assembly 44 and the end plate 20. However, at the other end ofthe air chamber 22, passages 76 are provided for the escape of air tothe atmosphere during movement of the piston assembly from the retractedposition adjacent end wall 20 to an extended position adjacent end wall18.

In operation, high pressure air from the source 36 is delivered througha first passage means comprising line 40, valve 38, line 42, and inlet32 to drive the piston assembly 44 from the position shown toward theother end of the cylinder. The connecting rod portion 112 is connectedto the device to be operated and its movement results in the desiredmovement of the device being operated. In association with a swingingarm press unloader, the swinging arm is moved upwardly from a downposition adjacent the press to an up position spaced outwardly from thepress as the piston assembly 44 moves from its lowermost positionadjacent end wall 20 to its uppermost position adjacent end wall 18. Asthe piston assembly 44 is extended upwardly, the oil cylinder 64 is alsomoved by sliding action in the bearing 74. During the upward movement ofthe piston, the outlet port 34 may be connected by line 44 through valve38 to exhaust line 45. When the piston assembly is to be returned to thestarting position, it is a feature of the present invention to connectthe inlet port 32 and line 42 to the outlet port 34 and line 44 throughthe valve 38 a first passage means comprising. Thus, as the piston isreturned to its starting position, air in the air cylinder is driventhrough the lines 42, 44 from one side of the piston assembly to theother side. The air undergoes a substantial temperature drop andprovides a low temperature cooling medium which is then utilized in theair cylinder to cool the oil cylinder casing.

When the oil cylinder is initially filled with oil with the oil cylinderin a vertical attitude in a retracted position, the oil enters throughthe passage 110, passage 128, and outlet 132. The oil level ismaintained approximately at 170 so as to provide a pocket of air abovethe oil which is subsequently mixed with the oil to providecompressibility in operation.

The oil cylinder also includes valve means in the form of a valveelement 174 which is slidably mounted on the support shaft 46 and biasedoutwardly in spaced relationship to the piston assembly 44 by a springelement 176 fixedly mounted on the piston assembly at one end and on thevalve element at the other end. The valve 174 is provided with a flatside wall 178 adapted to abut the side wall 180 of the valve body 90 andto close the ports 122 when the piston assembly 44 is moved upwardly tothe extended position. A centrally located annular groove 182 in valve174 is connected through the face 178 by a plurality ofcircumferentially spaced transversely extending passage means 184. Theaxial spacing of the groove 182 relative to the face 178 is such as tocommunicate with the outlet port 132 in the closed position of the valveagainst the face 180. Consequently, during return movement, highpressure oil coming through passage 132 will fill the groove 182 andtravel through passages 184 to react against the face 180 and positivelyseparate the valve 174 from the valve body 90. The valve 174 is mountedin an enlarged portion 186 of the oil cylinder chamber so thatsubstantial clearance is provided at 188 between the periphery of thevalve and the inner wall of the oil cylinder. In this manner, oil in thecylinder is able to flow around the valve as the oil cylinder movesrelative thereto in the latter stages of extension of the device. Whenthe valve 174 abuts the valve body 90, the piston assembly 44 will moveagainst the spring 176 toward the valve element 178 and a throttlingaction will occur as the oil flows through the restricted passage 188between the valve element and the enlarged portion 186 of the cylinderwall around the valve element 174 and the valve body which has acorresponding diameter. In this manner, the terminal portions of theupward movement are cushioned by the aerated oil in the oil cylinder andthe movement is decelerated at a controlled rate until the pistonassembly 44 bottoms against the valve 174.

Thus, the up operation of the device comprises delivery of high pressureair through the inlet 42 to the air cylinder 22 which causes the pistonassembly 44 to be moved from its normal retracted position, shown in thedrawing, adjacent the end wall 20 to an extended position adjacent theend wall 18. With the connecting rod 112 connected to a swinging arm ofa press unloader, the swinging arm is moved from a lowered positionadjacent a press bed to a raised position relative thereto. In order toreturn the swinging arm from the raised position to the loweredposition, the high pressure air is exhausted from the air cylinder andthe swinging arm is allowed to return to its lowered position bygravity. The oil cylinder is effectively divided into an upper and lowerchamber by the valve body 90 with the aerated oil being driven into theupper chamber during upward movement and into the lower chamber duringdownward movement. The rate of return of the swinging arm is controlledby the rate of flow of oil in the oil cylinder 12 from the upper chamberto the lower chamber.

More specifically, as the piston assembly 44 is moved to the extendedposition, the oil cylinder 64 is slidably displaced relative to thebearing 74 and relative to the sup port rod 46 and the valve body 90attached thereto. As the oil cylinder is extended, the shaft portion 96becomes disassociated from the sleeve 102 which, forming part of the oilcylinder casing, is also moved outwardly. As the piston assembly 44 isextended, the volume of the lower oil chamber diminishes while thevolume of the upper oil chamber increases. As the valve element 174 andthe wall portion 50 approach the fixed valve body 90, oil in the loweroil cylinder chamber is driven through the passages 122 and into theexpanding upper chamber on the other side of the valve body 90. Valve124 is main tained in the open position shown by the oil under pressureas it flows through the passages 122. After the shaft portion 96separates from the sleeve 102, the quantity of oil in the upper chamberis such as to provide a substantial depth of oil above the end of thepassage 128 in rod portion 96. When the piston assembly 44 approachesthe end of its outward movement, the valve element 174 comes intoabutting engagement with the valve body 90 and passages 122 are closed.The inside diameter of the oil cylinder is constant except at thecentral enlarged portion 186 which tapers gradually from the shoulder187 toward the piston assembly 44 for a substantial distance so as toprovide a gradually restricted opening around the valve 90. The enlargedportion of the enlarged portion of the oil cylinder at 186 moves by thevalve body 90 permitting the restricted flow of oil after the passages122 are closed and the piston assembly 44 continues movement toward thevalve body 90 aganist the bias of the compression spring 176 and theterminating movement of the swinging arm is cushioned by oil trappedbetween the piston assembly and the valve body 90 as outward movement isterminated. Air in the air compression cylinder is exhausted through theslots 76 in the bushing 74 and the line 44 may be connected to exhaustline 45 in the valve 38.

Return movement of the swinging arm is efiected by opening line 42 sothat the high pressure air can exhaust from the air cylinder through theport 32. The line 42 may be connected to exhaust or, preferably,connected to the line 44 to deliver the exhausting and cooled airthrough the port 34 into the air cylinder chamber to cool the oilcylinder. The swinging arm will move downwardly under gravity as thehigh pressure air is exhausted and the oil cylinder 12 and pistonassembly 44 will'be forced toward the end wall 20. As the downwardmovement of the swinging arm is started, the aerated oil in the upperchamber of the cylinder is immediately forced through opening 130 intopassage 128 and through passage means 132 to the groove 182 in the valveelement 174. The oil is delivered from the groove 182 by passage means184 into the face 180 of the valve body 90 to positively separate thevalve 174 from the valve body 90 and permit flow outwardly along theface 180 of the valve body to open passage 132 and bypass passage means126. In addition, the aerated oil initially flows around the valve body90 and the valve 174 until the enlarged portion 186 of the oil cylinderslides past the valve body. When the valve element 174 clears thepassage 132 and valve body 90 enters the narrow diameter portion of thecylinder, the rate of flow of oil from the upper portion of the oilchamber to the lower portions of the oil cylinder is controlled by theposition of the adjustable control rod 134. The valve element 124 isforced against the adjacent face of the valve body 90 at the beginningof the return movement to close the passages 122. Oil flows out of thepassage 132 into the expanding lower chamber at a rate suflicient tolower the swinging arm at the rate desired. Toward the end of downwardmovement of the piston assembly 44 and oil cylinder 64 toward theretracted position, the rod end 96 enters the chamber 110 which causesthe remaining aerated oil to be trapped between the valve body 90 andthe wall 66 so as to cushion and stop the downward movement of theswinging arm.

Among the many advantages of the present invention are:

(1) increased compactness reducing the space required for mounting ofthe parts on the machine with which it is to be utilized.

(2) Reduction in the number of assembly steps and assembly proceduresrequired to install the air-oil cylinder device on a machine with whichit is to be used.

(3) Reduction in stress on the air-oil cylinder and associated parts inuse by transmitting forces developed during raising and loweringmovements through a common central axis.

(4) Reduction in the overall length of the apparatus.

(5) Utilization of aerated oil to cushion both terminal portions of themovement.

(6) Reduction of leakage of oil by reducing the number of fittingsrequired for the oil system.

(7) Reduction of leakage of oil in the oil cylinder by reducing thenumber of scaled joints.

(8) Reduction of leakage of oil by cooling of the oil and the oilcylinder parts to reduce expansion. and contraction.

(9) Reduction of frost problems in the air cylinder by heating from theoil cylinder.

(10) Reduction in the number of total parts by combining the functionsof various parts.

' (l1) Eliminating the requirement for separate tie rods for the oilcylinder.

(12) Eliminating the requirement for a separate piston rod for the aircylinder.

It will be apparent to those skilled in the art to which this inventionrelates that the many advantages of the present invention may beotherwise obtained by various modification and change in the details ofconstruction of the illustrative embodiment. Accordingly, it is intendedthat the claims appended hereto be construed to include other apparatusand arrangements which utilize the inventive principles except insofaras limited by the prior art.

The invention claimed is:

1. Apparatus for moving a swinging arm of a press unloader or the likebetween a lowered position adjacent a press and a raised positionlocated outwardly away from the press comprising:

an air cylinder operable by high pressure air between a retractedposition and an extended position to move the swinging arm from thelowered position to the raised position and operable between theextended position and the retracted position to move the swinging 'armfrom the raised position to the lowered position,

an oil cylinder mounted within said air cylinder to cushion the terminalportions of the movement and to control the rate of movement between theextended position and the retracted position,

valve body means mounted in said oil cylinder and dividing said oilcylinder into upper and lower chamber portions and having flow passagemeans connecting said chamber portions, support rod means mounted withinsaid oil cylinder, valve means mounted on said support rod means andbeing cooperable with said valve body means to control flow of oilthrough said passage means between said upper chamber portion and saidlower chamber portion so as to cushion the terminal portions of themovements and control the rate of movement between the extended positionand the retracted position, said valve means comprising:

a first valve element slidably mounted on said support rod means on oneside of said valve body means and being movable into engagement withsaid valve body means to close said flow passage means during theterminal portion of the movement from the retracted position to theextended position, spring means spacing and holding said first valveelement in spaced relationship to said valve body means during the otherportion of the movement from the retracted position to the extendedposition and being compressible to hold said first 'valve element onsaid valve body means during the terminal portion of the movement, asecond valve element slidably mounted on said support rod means on theother side of said valve body means and being movable to an openposition relative to said flow passage means permitting free flow duringmovement from the retracted position to the extended position and to aclosed position relative to said passage means restricting free flowduring movement from the extended position to the retracted position. 2.Apparatus for moving a swinging arm of a press unloader or the likebetween 'a lowered position adjacent a press and a raised positionlocated outwardly away from the press comprising:

an air cylinder operable by high pressure air to move the swinging armfrom the lowered position to the raised position,

an oil cylinder mounted within said air cylinder to cushion the terminalportions of the movement and to control the rate of movement,

valve body means mounted in said oil cylinder and dividing said oilcylinder into upper and lower chamher portions and having flow passagemeans connecting said chamber portions, support rod means mounted withinsaid oil cylinder, valve means mounted on said support rod means andbeing cooperable with said valve body means to control flow of oilthrough said flow passage means, 1

said support rod means having a central longitudinally extending oilpassage providing for flow past said valve body means,

one opening for said oil passage being located on one side of said valvebody means,

and another opening for said oil passage being located on the other sideof said valve body means,

and a control rod mounted in said oil passage and being associated withone of said openings to control the rate of flow of oil through said oilpassage.

3. The invention as defined in claim 2 and wherein portions of said oilcylinder being of varying inside diameter and providing restricted flowpassages between said upper chamber portion and said lower chamberportion.

4. Apparatus for moving a swinging arm of a press unloader or the likebetween a lowered position adjacent a press and a raised positionlocated outwardly away from the press comprising:

an air cylinder operable by high pressure air to move the swinging armfrom the lowered position to the raised position,

an oil cylinder mounted within said air cylinder to cushion the terminalportions of the movement and to control the rate of movement,

valve body means mounted in said oil cylinder and dividing said oilcylinder into upper and lower chamber portions and having flow passagemeans connecting said chamber portions,

support rod means mounted within said oil cylinder,

valve means mounted on said support rod means and being cooperable withsaid valve body means to control flow of oil through said passage meansbetween said upper chamber portion and said lower chamber portion so asto cushion and control the rate of movement of said air cylinder,

said support rod means terminating in a shaft portion extending intosaid upper chamber portion,

said support rod means having a central longitudinally extended oilpassage providing for flow of oil past said valve means,

one opening for said oil passage being located on one side of said valvebody means in the end of said shaft portion,

another opening for said oil passage being located on the other side ofsaid valve body means,

and sleeve means mounted on said oil cylinder and being cooperable withsaid shaft portion to close said one of said openings to the upperchamber portion in the retracted position.

5. The invention as defined in claim 4 and having an oil filling passageprovided in said sleeve means.

6. The invention as defined in claim 4 and said sleeve means formingconnecting rod means for connecting said air cylinder to the swingingarm through said oil cylinder.

7. Apparatus for moving a swinging arm of a press unloader or the likebetween a lowered position adjacent a press and a raised positionlocated outwardly away from the press comprising:

an air cylinder operable by high pressure air to move the swinging armfrom the lowered position to the raised position,

an oil cylinder mounted within said air cylinder to cushion the terminalportions of the movement and to control the rate of movement,

support rod means mounted within said oil cylinder,

valve body means mounted in said oil cylinder and dividing said oilcylinder into upper and lower chamber portions and having flow passagemeans connected said chamber portions,

valve means mounted on said support rod means and being cooperable withsaid valve body means to control flow of oil between the upper chamberportion and the lower chamber portion so as to cushion and control therate of movement of said air cylinder,

said valve means comprising a valve element slidable on said support rodmeans,

a surface of said valve body means abuttingly engageable with said valveelement in one of said positions to close said flow passage means,

oil passage means in said support rod means extending through said valvebody means and connecting said lower chamber portion of said oil chamberto said upper chamber portion of said oil chamber,

an oil outlet passage in said support rod means located in alignmentwith said valve element in the abutting position against said valve bodymeans,

an oil passage means provided in said valve element and connected tosaid oil outlet passage to positively separate said valve element andsaid valve body means as movement begins from the one of said positionsto the other of said positions.

8. The invention as defined in claim 7 and wherein said oil passagemeans comprises an annular oil groove and transverse passage meansextending toward said valve body means. I

9. Apparatus for controlling the rate of movement of an associatedmovable mechanism. between an extended position and a retracted positionand for cushioning the terminal portions of the movement comprising:

a movable oil cylinder having axially spaced end wall portions and beingfilled with compressible aerated oil and connected to the movablemechanism and movable therewith,

fixedly mounted support rod means extending into said oil cylinder andsupporting said oil cylinder for sliding movement relative theretobetween an extended position and a retracted position,

valve body means fixedly mounted on said support rod means and dividingsaid oil cylinder into upper and lower chamber portions and having flowpassage means connecting said chamber portions,

valve means mounted on said support rod means and being cooperable withsaid valve body means to control flow of oil through said flow passagemeans between said chamber portions,

said valve means comprising:

a first valve element slidably mounted on said support rod means on oneside of said valve body means, i I

a spring means holding said first valve element in spaced relationshipto the adjacent end wall portion of said oil cylinder,

said first valve element being in an open position spaced from saidvalve body means in the retracted position and movable along saidsupport rod means with said oil cylinder during movement from theretracted position .to the 7 extended position to a closed position inengagement with said valve body means and restricting flow through saidHow passage means during the terminal portion of the movement from theretracted position to the extended position, 1

said spring means permitting movement of said oil cylinder relative tosaid first valve element after engagement of said first valve elementand said valve body means and compressibly holding said first valvemeans on said valve body means, first restricted passage means providingfor flow past said valve body means after engagement of said first valveelement with said valve body means to permit restricted flow around saidfirst valve element and said valve body means during the terminalportion of the movement from the retracted position to the extendedposition,

means for separating said first valve element from said valve body meansduring movement from the extended position to the retracted position andfor returning said first valve element to the open position,

a second valve element on the opposite side of said valve body meansmovable to an open position relative to said flow passage means duringmovement from the retracted position to the extended position and to aclosed position relative to said flow passage means during movement fromthe extended position to the retracted position.

a second restricted passage means providing flow past said valve bodymeans when said second valve element is in the closed position andcontrolling the rate of movement between the extended position and theretracted position,

and cushioning means etfective during the terminal portion of themovement from the extended position to the retracted position.

10. The invention as defined in claim 9 and wherein said secondrestricted passage means comprising an oil passage through said valvebody means connecting said chamber portions, an inlet opening spacedaxially beyond said valve body means and located in said upper chamberportion, and an outlet opening spaced axially beyond said valve bodymeans and located in said lower chamber portion.

11. The invention as defined in claim 10 and having adjustable fiowcontrol means associated with said oil passage to vary the rate of flowof oil therethrough to obtain a predetermined rate of movement of theassociated device.

12. The invention as defined in claim 11 and said second restrictedpassage means, oil passage and said flow control means being mounted insaid support rod means.

13. The invention as defined in claim 10 and wherein said secondrestricted passage means further comprises a bypass passage through saidvalve body means permitting restricted fiow from the upper chamberportion to the lower chamber portion when the second valve element is inthe closed position and the first valve element is in the open position.

14. The invention as defined in claim 10 and wherein said secondrestricted passage means further comprises a passage between the oilcylinder and the valve body means open during initial movement andclosed during the rest of the movement of the oil cylinder from theextended position to the retracted position.

15. The invention as defined in claim 14 and wherein the passage isformed by varying the inside direction of said oil cylinder.

16. The invention as defined in claim 15 and the upper portion of saidoil cylinder having a diameter substantially equal to the diameter ofsaid valve body means so as to prevent flow therebetween, and the lowerportion of said oil cylinder having a diameter greater than the diameterof said valve body means so as to permit flow therebetween.

17. The invention as defined in claim 16 and the lower portion of saidoil cylinder being tapered so as to provide a varying diameter defininga variable flow passage with said first valve means providing cushioningmeans as said oil cylinder is moved from the retracted position to theextended position.

18. The invention as defined in claim 9 and said cushioning means forcushioning the return movement from the extended position to theretracted position comprismg:

a plug member formed on the end of said support rod in the upper chamberportion, and

a sleeve member in said upper chamber portion and arranged to receivesaid plug member and trap and compress a portion of the aerated oiltherebetween during the terminal portion of the movement from theextended position to the retracted position.

19. The invention as defined in claim 18 and wherein said secondrestricted passage means comprising:

an oil passage in said support rod extending through said valve bodymeans and connecting said chamber portions,

an inlet opening in said upper chamber portion at the upper end of saidplug member, and

an outlet opening spaced axially beyond said valve body means andlocated in said lower chamber portion.

20. The invention as defined in claim 19 and wherein said first valveelement having passage means connectable to said outlet opening in theclosed position in engagement with said valve body means to provide forflow of high pressure oil from the upper chamber portion to the lowerchamber portion between the first valve element and the valve body meansto cause separation of the second valve element and the valve body meansas the return movement from the extended position to the retractedposition is started.

References Cited UNITED STATES PATENTS 2,746,557 5/1956 Augustin 9283,149,541 9/ 1964 Hunter et al 928 3,302,533 2/1967 Hutter et al. 928

FOREIGN PATENTS 149,708 1/ 3 Australia. 819,353 9/ 1959 Great Britain.

PAUL E. MASLOUSKY, Primary Examiner.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No.3,399,603 September 3, 1968 Harlan R. Cagle It is certified that errorappears in the above identified patent and that said Letters Patent arehereby corrected as shown below:

Column 3, line 48, "a first passage means comprising" should read toprovide a second air passage means Column 4, line 72, cancel "enlargedportion of the". Column 8, line 2, "connected" should read connectingColumn 10, line 49, Hunter et al." should read Hutter et a1.

Signed and sealed this 10th day of February 1970.

(SEAL) Attest:

WILLIAM E. SCHUYLER, JR.

Commissioner of Patents Edward M. Fletcher, Jr.

Attesting Officer

